The invention relates to a height adjustment device for a vehicle seat.
In order to better protect a vehicle occupant in the event of an accident, the occupant can belt himself in with a seatbelt. A conventional seatbelt is connected to the vehicle at at least two points. Three connection points between the seatbelt and vehicle are conventional, with a belt buckle for closing and opening the seatbelt being is in the region of one connection point. In the event of an accident, considerably increased forces may act on the connection points.
In modern vehicles, height adjustable seats, where the distance of a seat shell, on which the occupant can sit, from a vehicle floor can be adjusted by a height adjustment device, are conventional. It is advantageous for the occupants of these height adjustable seats if the belt buckle is fastened in the region of the height adjustable seat shell and follows the movements of the seat shell instead of being fastened to the vehicle floor. In such case, the belt buckle, independently of the set height of the seat shell, is at the same distance from an occupant sitting on the seat shell, which is not the case for a belt buckle fastened to the vehicle floor. In the case of a belt buckle provided in the region of a height adjustable seat shell, the force introduced via the belt buckle in the event of an accident has to be transmitted to the vehicle floor via the height adjustment device. The height adjustment device must be able to withstand this load, which is greatly increased by the accident. This can be achieved in conventional solutions by providing an additional component as force transmitting element in the force transmission path of the height adjustment device owing to the tensile force of the belt buckle in the event of an accident. This increases the load bearing ability of the height adjustment device. However, the additional component is required.
A height adjustment device for motor vehicle seats is known from German Patent Document DE 43 02 329 B4, in which the seat part can be raised and lowered relative to the vehicle floor by means of pivot supports that are articulated in the region of each seat corner and are connected together in pairs via pivot shafts. A single spindle mechanism serves for infinitely adjustable height adjustment of the seat part. A blocking device is locked or released as required via a lever mechanism linked to the height adjustment. The height adjustment device should also withstand a crash load.
German Patent Document DE 197 40 043 B4 describes a vehicle seat with a belt buckle of a seatbelt and with a height adjustable underframe on which a seat support is arranged. The height adjustable underframe has rear and front pivot supports that are articulated in each case to a pivot articulation on the seat support. The belt buckle is associated with the seat support. A blocking device is formed on the height adjustable underframe, which device, in the event of tension on the belt buckle due to an accident, is intended to reduce alteration of the height adjustable underframe that can occur due to the accident. The blocking device comprises the additional component mentioned above, which is included as force transmitting element in the force transmission path of the height adjustable underframe as height adjustment device.
A height adjustment device for seats is described in German Patent Document DE 31 30 280 A1, in which the seat part, by means of pivot supports arranged in the region of each seat corner and connected together in pairs via pivot shafts, can be raised and lowered relative to the vehicle floor by means of an adjustment device associated with each pivot shaft. A linearly extendable adjustment element as an adjustment device is mounted at one end pivotably on the one pivot shaft and is articulated at the other end to a pivot lever, which is connected in rotation resistant manner to the other pivot shaft.
A height adjustment device for seats with front and rear lever arms fastened in rotatable manner between a seat frame and a base is known from British Patent Document GB 2 018 583 A. A rod connects the one lever to the other one, the rod being fastened to one of the levers via a connecting element. The connecting element can be adjusted between two states. In one state, the rod can slide through the connecting element, so that the distance between the seat frame and the base can be changed. In the other state, the rod is connected securely to the connecting element, so that the distance between the seat frame and the base is fixed.
German Patent Document DE 36 36 786 A1 describes a height adjustment device for seats having a seat part that can be raised and lowered relative to the vehicle floor by means of pivot supports arranged in the region of each seat corner via an adjusting device. This adjusting device comprises a threaded spindle arranged in stationary manner in the axial direction in a mounting on the bearing body of the pivot supports, but is rotatable, which threaded spindle engages with its setting thread in a spindle nut associated with the adjustment arm of a pivot support. In order to be able to connect the spindle nut seated on the threaded spindle to the adjustment arm of the pivot support directly without the aid of intermediate members, the mounting that receives the threaded spindle in stationary manner in the axial direction is formed as a cardan-type mounting.
German Patent Document DE 203 06 680 U1 describes a device for locking an adjustment device of a vehicle seat in the event of an accident. The vehicle seat has, in addition to an adjustment device, a pretensioning device for pretensioning a seatbelt in the event of an accident. The pretensioning device is coupled with a first locking element such that triggering of the pretensioning device brings this first locking element into engagement with a second locking element, which locks the adjustment device. In this case, the seatbelt is coupled with the first locking element in such a manner that the belt force occurring in the event of an accident and when the pretensioning device is not triggered or is insufficiently triggered likewise brings the first locking element into engagement with the second locking element.
Exemplary embodiments of the present invention are directed to providing a height adjustment device for a vehicle seat that also withstands an increased load in the event of an accident.
A height adjustment device in accordance with the present invention comprises an adjustment parallelogram, which consists substantially of a seat frame part, an upper rail and lateral links. The lateral links connect the seat frame part and the upper rail in rotary articulated manner. A spindle drive can adjust the adjustment parallelogram indirectly or directly such that a distance between the seat frame part and the upper rail is changed by changing a length of the spindle drive.
The adjustment parallelogram forms part of a seat structure for a vehicle seat. In a conventional embodiment, the adjustment parallelogram is connected to a second adjustment parallelogram via one or more transverse tubes. In one embodiment a spindle drive may be omitted from the second adjustment parallelogram. Above the seat frame parts of the two adjustment parallelograms and the transverse tube or tubes there is usually a seat shell on which an occupant can sit. In conventional embodiments, the upper rails of the two adjustment parallelograms are mounted displaceably on lower rails fastened to a vehicle floor. This permits longitudinal adjustment of the vehicle seat along the lower rail. Further parts of the vehicle seat, such as, for example, a backrest are not crucial for the proposed solution, and will therefore not be explained further here.
A particular rigidity of the proposed height adjustment device is achieved in that the spindle drive connects together two obliquely opposing corners of the adjustment parallelogram in reinforcing manner. The connection can be carried out indirectly or directly. “Reinforcing” indicates here that the adjustment parallelogram with the spindle drive is capable of transmitting a greater force—introduced via an upper region of the adjustment parallelogram perpendicular to or in the direction of a longitudinal extent of the seat frame part—to the upper rail than would be the case without the spindle drive. In this case, no additional blocking device, which can obstruct a movement of the adjustment parallelogram, for example, due to a pivoting movement linked to the height adjustment, is required. Different embodiments may differ from each other, for example, by different points of articulation of the spindle drive to the adjustment parallelogram. Advantageous embodiments are distinguished in particular in that a distance between the seat frame part and upper rail substantially does not change upon the transmission of a force introduced as above in the case of an accident.
No change, or as small as possible a change, in the distance between the seat frame part and upper rail in the case of an accident is important, particularly when a belt buckle is attached in the upper region of the adjustment parallelogram, via which buckle an increased force as described above can be transmitted to the upper rail in the event of an accident. The more rigid the adjustment parallelogram, the more quickly can a counter force, which is necessary for restraining the occupant by means of the seatbelt, be built up in the case of an accident. The earlier the occupant is restrained by the seatbelt, the better can loads which are due to an accident be reduced for the occupant, since the occupant participates earlier in the vehicle deceleration due to an accident. The adjustment parallelogram, the spindle drive and the attachment of the belt buckle thereto have to be designed in terms of their load bearing ability for forces, which usually occur maximally in this region in the event of an accident. This means that the spindle drive has to be capable of bearing high loads, which, as described in the example of embodiment, applies in particular for tensile loading. The tensile loading acts in a direction in which the spindle drive would be extended, i.e. lengthened. A spindle drive capable of bearing high loads can, for example, be constituted by the use of at least one high strength material, or alternatively or in addition by larger dimensions of the load bearing components of the spindle drive, with sufficient tensile strength of the spindle drive having to be taken into account. In the spindle drive of the height adjustment device described in German Patent Document DE 43 02 329 B4, merely pressure loading of the spindle drive by the mass of the motor vehicle seat can be achieved. The pressure loading acts in a direction in which the spindle drive would be compressed, i.e., shortened. Linking of the height adjustment with the belt buckle is moreover not described in German Patent Document DE 43 02 329 B4.
In the event of an accident, the spindle drive must also not substantially twist, which would change its length. This can be ensured, for example, by a suitably flat pitch of the thread, taking into account frictional forces which act upon the adjustment. Common accidents are, for example, recreated by known crash tests, which crash tests and the imitation thereof in computer aided simulations can be used for designing the height adjustment.
Without departing from the scope of the solution in accordance with the proposal, further elements may be added to the adjustment parallelogram, as long as they do not appreciably impair the rigidity of the adjustment parallelogram. Further elements may for example be levers, deflectors, connecting parts, fittings or similar components.
Instead of a spindle drive, other embodiments of a rod type adjuster may also be used. A rod type adjuster is distinguished by a changeable length. Among other things, a piston drive, such as, for example, a hydraulic or a pneumatic piston, may be used. Likewise, mechanical or electromechanical thrust elements are possible. The constituents of the adjustment parallelogram and adjoining components serve, in particular, for mechanical strength in the context of the present invention. These constituents may also be otherwise named and embodied in this context.